Hi-Standard produced a couple of different fighting shotguns. There is a good article on them in the excellent reference work The World's Fighting Shotguns by Thomas Swearengen.
All of their pump action fighting shotguns are based on the Flite King action. They include the Type 8104, extended -magazine Type 8104 (never catalogued), Type 8111, Type 8113, and the Type 8246 (Air Force trials gun).
They are solid shotguns with their main downfall being that the barrel is permanently attached to the receiver (no removeable/replaceable barrels) and a single action bar.
Not sure on supplies of extra parts, haven't researched that aspect.